Field of the Invention
The present invention relates to a process of producing a heating element.
Description of Related Art
Thermal-film fixation type fixing devices are known as fixing devices employed in image forming apparatuses such as copiers and laser beam printers. Such fixing devices can shorten a time from turn-on to copy start (warming-up time), and are advantageous in terms of energy saving.
The fixing devices include a heating belt (heating element) that generates heat in response to supply of electricity to the heating belt. The heating belt is, for example, a seamless belt including a film made of a heat-resistant resin such as polyimide and a releasing layer made of fluororesin or the like that covers the outer peripheral surface of the film. As such a heating belt, a belt is known in which a belt-shaped substrate comprising the heat-resistant resin contains conductive fibrous fillers that satisfy a certain condition for the purpose of reducing the resistance of the heating belt or increasing the stability of the resistance (see, for example, Japanese Patent Application Laid-Open Nos. 2012-8299 and 2013-25120).
The heating belt disclosed in Japanese Patent Application Laid-Open No. 2012-8299 can sufficiently reduce the initial resistance value thereof. In addition, the heating belt disclosed in Japanese Patent Application Laid-Open No. 2013-25120 can provide a high resistance stability in comparison with conventional belts. However, the resistance value may increase with time even when these heating belts are used, and utilization of the heating belts in the fixing device of an image forming apparatus may result in uneven fixing due to changes in resistance value in the heating belt.